[http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1446474 American Journal of Public Health, June 2001, Vol. 91, No. 6, pages 956-957]</ref>}} | [http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1446474 American Journal of Public Health, June 2001, Vol. 91, No. 6, pages 956-957]</ref>}} |